SMR 1829-16 Winter College on Fibre Optics, Fibre Lasers and Sensors 12-23 February 2007 Passive Fibre Components (PART 2) Walter Margulis Acreo, Stockholm Sweden
Passive Fibre Components W. Margulis walter.margulis@acreo.se Examples Couplers/Splitters Optical Taps Multiplexers/combiners Demultiplexers/splitters Fixed Add/drop Multiplexers Interleavers Photonic Lightwave Circuits [AWG] Twin Core Fibers Connectors Isolators Circulators Optical Attenuators Polarisation Related Components Polarization related problems Tunable Filters Interferometers Polarization control (active) Polarization switch Electrooptical fibers 1
Cleaving fibers 125 µm Splicing Splicing station Splice protection Hand-held 2
Attenuators 1x1 splitter Fiber connectors Various Types: FC/PC, SC, LC, SMA, ST Polishing quality: SPC (Super), UPC (Ultra) Fiber Alumina ferrule 8 PC = Physical Contact Insertion loss 0.2 db Back reflection 20 db APC = Angled Physical Contact Insertion loss 0.2 db Back reflection 40 db 3
Effect of angle Angle-polished connectors APC (angled physical contact) Collimators Fiber pigtail Grin lens Collimated light 4
Microbenches Fiber components Miniature bulk optics (polarizer, isolator, filter) Tunable filters Narrow bandwidth (0.8 nm) High tuning resolution (0.05 nm) Broad tuning range (1535 1565 nm) Low insertion loss (1.5 db typical) Low back-reflection (-50 db max) 5
Polarization Types of polarization Linear polarization Eliptical polarization Circular polarization y y y x x x Polarization terms PDL - Polarization dependent loss (PDG Pol. dep. gain): The component has an insertion loss that depends on the state of polarization e.g., LiNbO 3 modulator: PDL ~2.5 db (compensated ~1 db) Polarizer: PDL ~50 db DGD Differential goup delay The component has a different optical path for the two principal polarization axis. e.g., HiBi (PM) fiber: DGD ~1 ps/m Standard fiber: DGD ~0.001 ps/m PMD Polarization mode dispersion Average value of the expectation value of DGD (could average in time, temp, ) e.g, the PMD of good cable could be 4 ps 6
Poincaré Sphere representation Moving fiber changes the state of polarization Polarization analysis: polarimeter 7
Mechanical polarization controllers Mickey mouse polarization controllers /4, /2, /4 plates Polarization splitter/combiner Long fiber coupler where each polarization couples to one fiber Polarization splitter/combiner Polarization splitter/combiner Extinction ratio >20 db Can combine pumps for laser 8
PMD of a fiber link Different time of flight Fiber irregularities causing polarization mode coupling Two polarizations with different group velocities The signal becomes smudged and unreadable to the receiver PMD compensation Tx Fibre link Polarisation Control PMD mitigated signal Delay Data acquisition & Control system PMD mitigator 9
DGD Fixed differential group delay Fixed differential group delay a length of HiBi fiber Adjustable: -45 to +45 ps in 0.5 ms Fiber polariser Typical extinction ratio: 40 db 10
PDG in Raman amplifiers The impact of pump polarization on the Raman PDG, Sergei Popov at al, J. Opt. A: Pure Appl. Opt. 6 (2004) S72 S76 De-polarisers Destroy polarization coherence with long PM fiber Improve performance of Raman Amp. 11
Optical activity (circular birefringence) Chiral Photonics Faraday Rotator Microbench Faraday rotator 12
Faraday rotators Material properties required: High Verdet constant (magneto-optical) Low absorption coefficient High damage threshold Low nonlinear response (prevent self-focusing, SPM) Typical materials: Terbium doped borosilicate glass, Tb gallium garnet (0.7-1.1 µm) Yttrium Iron Garnet (YIG) (1.3-1.5 µm) Typical isolation: >30 db http://en.wikipedia.org/wiki/faraday_isolator Faraday rotator mirror Reflected light is rotated by 90 o in relation to input light everywhere in the fiber 13
Typical application of Faraday rotator 3 db Michelson Polarization sensitive Polarization independent 3 db Michelson Faraday mirror Faraday mirror Fiber isolator Faraday rotator Faraday rotator 14
Polarization insensitive fiber isolator Faraday rotator Faraday rotator Puzzle from 1900 Can a closed black cavity with a single isolator as window cool the cavity to zero Kelvin by emission of radiation without work? http://www.usna.edu/users/physics/mungan/scholarship/faradayisolators.pdf 15
Microwave Circulator Microwave circulator (parenthesis) Based on the Faraday effect in magnetic materials 16
Optical Circulator Principle of operation Fiber circulator 2000 miracle 17
Arrayed Waveguide Gratings (AWG) AWG are useful devices in Wavelength Division Multiplexing (WDM) optical communication systems. An AWG is a device which can separate or combine channels with different wavelengths. http://en.wikipedia.org/wiki/array_waveguide_grating AWGs fabricated with silica-on-silicon technology Courtesy: Lech Wosinski (KTH, Stockholm) 18
BPM simulation of focusing in the second section 19
AWG 20
Optical characteristics of AWG 100 GHz 12-23 Feb 2007 Passive fiber components 2 W. Margulis AWG performance example (Datasheet) 12-23 Feb 2007 Passive fiber components 2 W. Margulis 21
Summary Splicers, connectors, attenuators Collimators and microbenches Example: tunable filter Polarization; PDL, DGD, PMD Pol. Control, Pol. Splitter, Polarimeter PMD mitigation DGD Polarizers, de-polarizers Optical activity and Faraday rotation Rotators, Isolators, Circulators MMI and AWGs 22